Based on archival images from the Hubble Space Telescope, stellar photometry of the galaxy NGC 4068 was carried out. The resulting Hertzsprung-Russell diagram (CM diagram) shows branches of young and ...old stars. To estimate the metallicity of young stars, isochrones of different ages and metallicities were used. A combination of isochrones and the CM diagram of stars shows that the young stars of NGC 4068 have high metallicity, up to the metallicity of the Sun (
). Since stars of high metallicity are observed throughout the body of the galaxy, we can talk about high metallicity of the entire galaxy, and not just one local region. The position of NGC 4068 among 105 irregular galaxies of different metallicities is shown on a diagram of the dependence between the metallicities of old and young stars. The almost linear dependence between these parameters indicates the absence of processes of rapid enrichment of galaxies with metals at the present stage of their evolution. The obtained results do not confirm the conclusion about the low metallicity of NGC 4068 reported earlier. For direct measurements of the metallicity of NGC 4068, the coordinates and fields of identification of the three brightest red supergiants with a high color index
, which indicates their high metallicity, are presented.
At the last deglaciation Earth's largest biome, mammoth-steppe, vanished. Without knowledge of the productivity of this ecosystem, the evolution of man and the glacial–interglacial dynamics of carbon ...storage in Earth's main carbon reservoirs cannot be fully understood. Analyzes of fossils 14C dates and reconstruction of mammoth steppe climatic envelope indicated that changing climate wasn't a reason for extinction of this ecosystem. We calculate, based on animal skeleton density in frozen soils of northern Siberia, that mammoth-steppe animal biomass and plant productivity, even in these coldest and driest of the planet's grasslands were close to those of an African savanna. Numerous herbivores maintained ecosystem productivity. By reducing soil moisture and permafrost temperature, accumulating carbon in soils, and increasing the regional albedo, mammoth-steppe amplified glacial–interglacial climate variations. The re-establishment of grassland ecosystems would slow permafrost thawing and reduce the current warming rate. Proposed methods can be used to estimate animal density in other ecosystems.
► Animal in mammoth steppe was as high as in African savannah. ► This ecosystem played important role in shaping planets environment. ► Mammoth steppe went extinct not because of climate. ► Restoration of this ecosystem is possible.
We analyze the reasons for imaging in the
and
filters to measure the distances to galaxies by the TRGB method. We show the possibility of using the TRGB method if Hubble Space Telescope (HST) images ...only in one F814W (
) filter are available. Based on archival HST images, we have carried out stellar photometry for 12 galaxies: NGC 1058, NGC 1365, NGC 1448, NGC 3079, NGC 3810, NGC 4321, NGC 4328, NGC 4485, NGC 4490, NGC 4651, NGC 6951, and NGC 7331, and measured their distances by the TRGB method. For many of the galaxies from this list such measurements have been made for the first time. A comparison of our results for galaxies with known TRGB measurements has shown good agreement.
The review focuses on the energetic and regulatory role of proton potential in the activity of chloroplasts, the light energy-converting organelles of plant cells. Mechanisms of generation of the ...transmembrane difference of electrochemical potentials of hydrogen ions
in the chloroplast thylakoid membranes are considered. Methods for measuring the intrathylakoid pH in chloroplasts are described. It is shown that under conditions of phosphorylation in chloroplasts, the pH of the intrathylakoid space decreases moderately (pH
in
⩾ 6.0–6.2, at the stroma pH
out
∼ 7.8–8.0), with a corresponding concentration component of
equal to ΔpH ⩽ 1.6–2.0. On analyzing the energy and structural features of ATP synthase of chloroplasts, we conclude that the energy stored as the concentration component of the proton potential ΔpH is sufficient to sustain ATP synthesis. The mechanisms of pH-dependent regulation of electron transport in chloroplasts (photosynthetic control of electron transport, enhancement of non-photochemical quenching of chlorophyll excitation in the light-harvesting antenna, light-induced activation of the Calvin-Benson cycle reactions, activation of ATP synthase) are considered briefly.
Based on archival Hubble Space Telescope images, we have performed stellar photometry of several fields in the isolated spiral galaxies NGC 6503 and NGC 6946 with high peculiar velocities. Based on ...the TRGB method, we have determined the distances to the galaxies:
D
= 6.30 ± 0.10 Mpc for NGC 6503 and
D
= 6.72 ± 0.15 Mpc for NGC 6946. The current stellar content of the galaxies does not differ from that of other similar galaxies. The metallicity for young stars in NGC 6503 is
Z
= 0.02 (corresponding to the solar metallicity), while the metallicity for stars in NGC 6946 reaches
Z
= 0.05. Very few old globular clusters have been found in NGC 6946, while they have not been found at all in NGC 6503. The number density distribution of stars with different ages in NGC 6503 does not differ from the analogous distributions in other galaxies. The large sizes of the thick disk in NGC 6503, which is clearly seen up to 6 kpc from the galactic disk plane and whose possible extension is noticeable up to 8.6 kpc from the plane, are a difference. The sizes of the region occupied by red giants of the disk in NGC 6503 are 51 × 17 kpc, which are not much larger than the sizes of this galaxy from H I radio observations.
The process of neutrino interaction with
and
nuclei is studied with allowance for the effect of charge-exchange resonances. The results obtained by calculating the cross section for solar-neutrino ...capture by the isotopes
Mo and
Mo,
, are presented. Use is made of both experimental data obtained for the strength functions
in (
) and (
He,
) charge-exchange reactions and the strength functions
calculated within the theory of finite Fermi systems. The effect of the resonance structure of
on the calculated cross sections for solar-neutrino capture is studied, and the contribution of each high-lying resonance to the capture cross section
is isolated. The contributions of all components of the solar neutrino spectrum are calculated. The contribution of background solar neutrinos to the double-beta decay of
Mo nuclei is estimated.
Images of 10 galaxies in F814W and F606W filters obtained on the Hubble Space Telescope (HST) are used to construct color-magnitude diagrams for the star population of these galaxies. The distances ...to the galaxies are estimated from the luminosity of the tip of the red giant branch. The galaxies examined here have radial velocities from 250 to 760 km/s relative to the centroid of the Local Group and distances ranging from 3.7 to 13.0 Mpc. Several other observed galaxies with low radial velocities are noted at distances beyond the limit of 13 Mpc.
The mathematical modeling is used to study the dynamics of solution deionization by sorption on aerogel electrodes. The matter transport by solution flow, diffusion, and sorption in pores are ...simulated. Several models are proposed to describe the phenomenon with different degree of approximation. Problems arising in numerical computing and ways to solve them are described. It is shown that at low solution concentrations and a small pore size the effect of electro-sorption is not reduced to the formation of a double electric layer on the pore surface, which uptakes ions from the solution. In addition to the formation of this layer distributed ionic charge is accumulated all over the pore space. The dependence of the effective diffusion coefficient inside the porous electrode on the ion concentration is found. Examples of calculating the deionization process at one-cycle and multi-cycle sorption are given.
In patients with schizophrenia, the thermal balance of the cerebral cortex was studied by means of microwave radiothermometry method and compared with the markers of systemic inflammation and ...clinical features of the disease course during therapy. Low temperature heterogeneity of the cerebral cortex was associated with an increase in the activity of inflammatory markers in the blood and, in most cases, with a positive response to therapy. High temperature heterogeneity of the cerebral cortex was typical of patients with insufficient activity of the inflammatory proteolytic system, high levels of antibodies to brain antigens, a more severe course of the disease and, in most cases, with resistance to therapy. A conclusion was made about the diagnostic value of the study of the thermal balance of the brain in patients with schizophrenia.
Stellar photometry for three fields in the Virgo cluster of galaxies has been performed on the basis of archival Hubble Space Telescope ACS/WFC images. The densely populated red giant branches ...belonging to cluster galaxies are seen on the constructed Hertzsprung–Russell diagrams. The distances to eight galaxies in the Virgo cluster have been determined by the TRGB method. The sizes of the stellar subsystems and the gradients in the number density of red giants along the galactic radius have been determined for the investigated galaxies. The stellar periphery of the galaxies has been found to extend to great distances and to cover the entire area of the images used. Therefore, the stars that have previously been thought to be intracluster stars actually belong to the periphery of neighboring galaxies.
